LEIBNIZ TO LANDGRAVE ERNST VON HESSEN-RHEINFELS

[A II 1, p544]

...I have still not seen either Father Malebranche's book on ideas,1 or Mr Arnauld's two books on this subject.2 Father Malebranche, author of de la recherche de la verité,3 is very clever and has some very good and solid thoughts, but he has others which are a little hyperbolic and rashly conceived. In some way, he follows Descartes' footsteps, but even Descartes does not satisfy me on these matters. Their principle (that everything that can be concluded from the idea one has of a thing can be truly attributed to it) is very questionable, and unless they give signs of a distinct conception it is pointless to say that everything one conceives clearly and distinctly is true. This analysis of our thoughts is of great importance, as much for judging as for inventing. And I have given my views on this in a short paper published in the November 1684 issue of the Acta Eruditorum of Leipzig, p537,4 about which I would be delighted to learn Mr Arnauld's opinion. I do not doubt that Your Serene Highness receives these Acts from time to time. They are printed every month and are rather well made. Some of those who work on them are my friends.